202 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 19 



Family SABELLIDAE 



Genus Euchone Malmgren, 1866 



Euchone arenae, new species 

 (Plate 6, Figs. 1-6) 



Collections: Sta. 2788 (23, TYPE) ; Sta. 2417 (2). 



The body is short, thick, tumid and tapers posteriorly. It measures 

 3.8 mm long without, and 6.2 mm long with, the tentacular crown ; 

 width is 0.7 mm. Segments include 8 thoracic and 13 to 15 abdominal 

 setigers ; each is biannulate. A narrow, glistening white band, behind the 

 second setigerous fascicle, surrounds the body. The tentacular crown is 

 well developed ; it consists of five to seven pairs of radioles, and two pairs 

 of long slender filaments at the ventral ends of the radiolar base (of 

 which only one is shown in Fig. 1 ) . Peristomial eyes are not visible, but 

 may be faded. A palmate membrane comprises less than a fourth of the 

 radiolar length ; it is inconspicuous. A pair of reddish eyes is visible in 

 the pygidium, in some individuals. 



The thoracic collar is continuous all around and of uniform length; it 

 is deeply cleft middorsally, where it joins the thoracic segment ; a slight 

 midventral cleft is distinguishable. 



The collar segment resembles those farther back but lacks neuro- 

 setae. Its notosetae are slender, limbate and number four or five in a 

 fascicle. More posterior thoracic notopodia have setae of two kinds; 

 three or four in superior position are long, limbate (Fig. 2), and four 

 to six are short, subspatulate (Fig. 3). The corresponding neuropodia 

 have long-handled imcini, in which the distal end is a large fang (Fig. 

 4) surmounted by three smaller teeth in a row. 



Abdominal parapodia have thick, short uncini in notopodia; they 

 number six to eight in a row ; each has a thick, broad base, a large curved 

 fang surmounted by three or four rows of small denticles, in transverse 

 rows (Fig. 5). The corresponding neuropodia have capillary setae, num- 

 bering three to five in a fascicle. 



The posterior end terminates in an anal groove (Fig. 6) in which the 

 last six setigerous segments are involved ; this may be broadly open, as 

 shown in the figure, or somewhat curled inward. The groove is followed 

 by a small triangular pygidium with dorsal anal pore. 



Euchone arenae differs from known species of the genus in having 

 six setigerous segments in the anal groove. Thoracic notosetae are essen- 

 tially of one kind, with the superior longer and less curved but otherwise 

 similar to the inferior shorter ones. 



